Using the transition state of a superconductor to produce energy

ABSTRACT

A method of using a superconductor to generate energy. The superconductor is alternated between a temperature above and below a critical temperature defined by a transition between the superconducting and non-superconducting state. The superconductor interacts with a magnetic field as the superconductor changes states. Energy is harnessed by coupling with the magnetic field as its strength fluctuates. The method would be particularly suitable for harnessing solar energy in space.

FIELD OF THE INVENTION

The invention pertains to generating energy using a superconductor, andin particular to generating energy by interacting the superconductorwith a magnetic field and cycling the superconductor through itstransition temperature.

BACKGROUND OF THE INVENTION

Since the discovery in 1911 that mercury is electrically superconductivewhen cooled to 4° K, many materials have been shown to becomesuperconductive below some critical temperature or transitiontemperature T_(c).

Superconductors are divided into type 1 and type 2. Type 1superconductors tend to have a low T_(c) and the transition between thenon-superconducting and superconducting state typically occurs over atemperature span of less than 1° K. Type 1 superconductors are mainlypure metals that conduct electricity at room temperature. All type 1superconductors only become superconducting at temperatures within lessthan 20 degrees K of absolute zero. Examples are tungsten (T_(c)=0.15°K), titanium (T_(c)=0.40° K), aluminum (T_(c)=1.175° K), tin(T_(c)=3.72° K) and lead (T_(c)=7.2° K). All these values are at normalpressures. The type 1 material with the highest known T_(c) is sulfur,for which T_(c) is about 17° K; however, sulfur needs to be compressedto 930,000 atmospheres to become superconducting and 1.6 millionatmospheres to achieve a T_(c) of 17° K.

In type 2 superconductors, the transition between states usually extendsover a broader range of temperature, typically 5° K. While type 1 andtype 2 T_(c) values overlap, the majority of type 2 materialssuperconduct at much higher temperatures than any type 1 material andinclude the so-called “high-T_(c)” superconductors, which are typicallyceramic materials. Examples of type 2 superconductors are the elementsvanadium (T_(c)=5.4° K), technetium (T_(c)=7.8° K) and niobium(T_(c)=9.25° K). These and all further values of T_(c) will beunderstood to be at atmospheric pressure.

The first superconductive wire was composed of Nb_(0.6)Ti_(0.4). Thefirst ceramic superconductor discovered, in 1986, wasLa_(0.85)Ba_(0.15)CuO₄, with a T_(c) of 35° K). A common high-T_(c)material is the compound YBa₂Cu₃O₇, often referred to as “YBCO” or“123”. YBCO has a T_(c) of 93° K. The highest T_(c) currently known is138° K for the compound Hg_(0.8)Tl_(0.2)Ba₂Ca₂Cu₃O_(8.33). Practicalapplications have been sought for superconductive materials. One use isin power transmission, in which the absence of electrical resistancewould significantly reduce power losses. Power transmission over longdistances is precluded by the requirement to maintain low temperaturesby some means such as using liquid nitrogen. There have been specializedcommercial applications; for example, power transmission over relativelyshort distances through limited spaces such as tunnels is greatlyincreased by using superconductors, to a degree not achievable by usingconventional power cables.

Other behaviors are associated with superconductivity, in particular theMeissner effect, whereby an article in a superconductive state canstrongly deflect a magnetic field; the superconductor and a magnet willproduce a mutually repulsive force. This effect is used in magneticlevitation (maglev) transportation systems that are in development.

SUMMARY OF THE INVENTION

Hitherto, superconductors have been applied for practical usesubstantially under steady state conditions; that is, they aremaintained in a superconducting state. The present invention disclosesengines for producing usable energy by cycling a superconductorrepeatedly through a transition region between a superconducting and anon-superconducting state, by alternately cooling and heating thearticle through T_(c). In the presence of a magnetic field, this causesthe strength of the field to vary at a given point. Coupling an energyconversion means with the magnetic field provides a way of generatingusable energy. Embodiments are disclosed in which mechanical andelectrical energy are generated.

It will be understood that the term “generating” is used in an acceptedsense of producing energy in a usable form, which strictly refers toharnessing one form of energy and converting it to another form which ismore appropriate for a contemplated use. For example, chemical ornuclear energy can be released from an appropriate fuel as thermalenergy. Thermal energy can be harnessed as mechanical energy to drive avehicle or an electrical generator. Electrical energy can be transmittedover long distances, then reconverted to other forms of energy such asmechanical or thermal energy as required. Each step in a chain of energyconversion involves some inefficiency with a consequent loss of energy.

In the present invention a superconductor is heated and cooled throughT_(c) so that it cycles between the superconducting and anon-superconducting state, in the presence of a magnetic field producedby a magnet. The magnetic field strength at a given point consequentlyfluctuates. This fluctuation can be translated into mechanical energy byallowing the superconductor and magnet to repel each other. A movablearm is attached to either the superconductor or the magnet.

The fluctuation also be translated into electrical energy. An electricalcurrent can be induced in a conductor such as a wire or coil directlyexposed to the fluctuating magnetic field strength. Alternatively, apiezoelectric body can be coupled with either the superconductor or themagnet, so that it responds to a fluctuating force therefrom; theelectrical conductor can be connected to the piezoelectric body toaccept the electrical current therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the levitation of a magnet by an article ina superconducting state.

FIGS. 2(a), 2(b) and 2(c) are schematics of an engine for generatingmechanical energy from the transition of a superconducting articlebetween a non-superconducting and a superconducting state, the enginebeing shown in different operating positions.

FIG. 3 is a resistivity-temperature curve showing a transition of asuperconductor through a transition temperature.

FIG. 4 is a diagram of the engine of FIG. 2 in accordance with a secondembodiment of the invention, the engine configured also to generateelectrical energy.

FIGS. 5(a) and 5(b) are diagrams of an engine in accordance with a thirdembodiment in which the electrical energy is generated by alternatelyexposing the superconducting article to and shielding it from thermalradiation.

FIG. 6 shows the engine of FIG. 5 with a mask intended to alternatelyexpose the superconducting article to and shield it from radiation.

FIG. 7 shows the mask of FIG. 6 configured to have alternate heatabsorbing and heat reflecting segments.

FIGS. 8(a) and 8(b) are diagrams of a portion of the engine of FIG. 5showing an electrically conductive coil embedded in the superconductingarticle in the non-superconductive and the superconductive staterespectively.

FIG. 9 is a diagram of a portion of the engine of FIG. 5 wherein a gridof conductive wires is disposed into a surface of the superconductivearticle.

FIGS. 10(a) and 10(b) are diagrams of an engine in accordance with afourth embodiment having a liquid crystal shutter controlled by feedbackfrom the released electrical energy, the shutter alternatelyintercepting and passing radiation.

FIG. 11 is a diagram of an engine in accordance with a fifth embodimenthaving a piezoelectric element for releasing the electrical energy.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, terms such as “superconductor” or“superconducting article” are understood to refer to an article having asuperconducting and a non-superconducting state. The terms are notintended to define whether or not the article is currently in thesuperconducting state.

This invention relates to generating energy using a superconductingarticle 100 by coupling with a magnetic field 102 that changes as aresult a transition of the article between the states, such that themagnetic field strength at some given point fluctuates.

Superconductors when in a superconducting state will strongly interactwith a proximate magnetic field 102. This phenomenon is manifested bythe well-known Meissner effect, in which a magnet 104 is levitated bythe repulsion from the superconducting article 100 below T_(c), asillustrated in FIG. 1. Above T_(c), interaction between thesuperconductor and the magnetic field is no stronger than with othercomparable materials. For example, a ceramic superconductor in thenon-superconducting state will behave like a conventional ceramicmaterial.

Therefore, during the transition of the superconducting article 100between states, the strength of the magnetic field at a given locationwill change. It is possible by coupling with the changing magnetic fieldto extract usable energy. In all embodiments of the invention, thetransition is caused by cooling or heating the superconducting article100 through T_(c).

A first embodiment of the invention generates mechanical energy. Anengine 110, shown schematically in FIG. 2, includes a movable mechanicalmember such as a beam 114 supported by a fulcrum 112. Thesuperconducting article 100 is attached to one end of the beam 114 and acounterweight 116 is attached to the opposite end.

The article 100 is suspended directly above the magnet 104 contained ina liquid-nitrogen cooling bath 118, the magnet 104 being orientedvertically, that is, with its poles aligned up and down. The beam 114 isfree to swing about the fulcrum 112 between first and second positions.In the first position, the article 100 is spaced well apart from themagnet 104 and also well clear of the cooling bath 118. In the secondposition, the article 100 is in close proximity with the magnet 104 andis placed in the cooling bath 118, or close enough to be cooled thereby.

The superconducting article 100 is selected to have a T_(c) higher thanthe temperature of the cooling bath, which in the present case isdefined by the boiling point of liquid nitrogen, 77° K. In other words,the bath 118 can cool the article to below T_(c). In the engine 110, thematerial selected for the superconducting article is YBa₂Cu₃O₇, (YBCO)which has a T_(c) of 93° K, although it could be any superconductingmaterial with a sufficiently high T_(c). Other possibilities includeYBa₄Cu₇O₁₅ (T_(c)=93° K) Bi₂Sr₂CaCu₇O₉ (T_(c)110° K) and HgBa₂Ca2Cu₃O₈(T_(c)=123-124° K). The resistivity-temperature curve for YBCO is shownin FIG. 3. The YBCO composition is typical of ceramic superconductors inthat it is an insulator above T_(c). Whatever cooling means is used, itmust correspond with a superconducting material having an appropriateT_(c). At present, the upper temperature limit of potential coolantsmust be below 138° K, the highest T_(c) currently known (forHg_(0.8)Tl_(0.2)Ba₂Ca₂Cu₃O_(8.33)).

The engine 110 works as follows. With the superconducting article 100above its transition temperature, the beam 114 is balanced so thatgravity is just sufficient to bring the article 100 into the coolingbath 118 and into close proximity with the magnet 104. Once the article100 has cooled below the transition temperature, it reflects themagnetic field of the magnet 104 as a mirror image. This produces arepulsive force, so that the superconducting article 100 moves away fromthe magnet 104 and out of the cooling bath 118. The ambient temperaturebeing higher than the transition temperature, the article 100 warms upsufficiently to lose its superconductivity. It no longer reflects themagnetic field of the magnet 104, and the repulsive force decays.Gravity brings the article 100 back into the cooling bath 118 and intoclose proximity with the magnet 104, for the cycle to be repeated. Thebeam 114 can continue to oscillate indefinitely as long as the coolingbath is maintained below T_(c). In effect, energy originally consumed inliquefying the nitrogen is released as mechanical energy.

In a second embodiment shown in FIG. 4, the counterweight 116 is asecond magnet 120 next to which is disposed an electrically conductivewire 122, which could be a coil. With oscillation of the beam 114, thesecond magnet 120 moves relative to the wire 122, and a resultingvariation in magnetic flux 121 at the wire 122 induces an alternatingelectrical current therein detectable with a meter 124.

In a third embodiment, an assembly 126 is constructed wherein thesuperconducting article 100 and a magnet 104 are fixedly spaced by adistance within which the undeviated magnetic field of the magnet 104extends to the superconducting article 100. The conductive wire or coil122 is disposed in the undeviated magnetic field, as illustrated in FIG.5(a). When the article 100 is cooled to below T_(c), it becomessuperconducting and reflects the magnetic field of the magnet 104, thussetting up a mutual repulsion. The resultant deviated magnetic fieldbetween the article 100 and the magnet 104 is illustrated in FIG. 5(b).

Thus, an alternating current is induced in the wire 122 as it is exposedto a varying magnetic field when the article 100 goes through thetransition between states.

This effect could be executed by intermittent thermal irradiation of thearticle 100, such that it would be above T_(c) when irradiated and belowT_(c) when not irradiated. This would be particularly achievable in aspace environment, as illustrated in FIG. 5. The assembly 126 would beallowed to spin so that the superconducting article 100 alternatelyfaced towards and away from the sun 150.

The third embodiment could be modified to provide for thesuperconducting article 100 to face the sun at all times, beingalternately exposed to solar radiation and shielded by a movable mask140. This could for example be a disc rotating about an axisperpendicular to the exposed face of the article, the disc havingalternate open and solid segments as in FIG. 6, or it could be a slat(not illustrated) rotating about an axis generally parallel to theexposed face of the article. The rotating disc might also be entirelysolid with alternating heat reflective segments 142 and heat absorbingsegments 144, as in FIG. 7. This could provide an advantage comparedwith an array of conventional solar cells, for example since the soliddisc would provide protection from damage by foreign particles of spacedebris.

A modified structure of the third embodiment is illustrated in FIG. 8.Here, the wire or coil 122 is embedded inside the article 100, as can bedone in the case of a ceramic superconductor by conventional ceramicforming techniques. In FIG. 8(a), the article is in thenon-superconducting state, with the magnetic field 102 passing throughthe article undeviated. In FIG. 8(b) the article is in thesuperconducting state and the magnetic field 102 is deviated around thearticle. In another modification shown in FIG. 9 a series of fineconductive wires in the form of a grid 128 could be pressed into thesurface of the superconducting article 100 which could be in the form ofa thin layer.

The generation of alternating electrical current in the coil 122 bycycling the article 100 between the superconducting andnon-superconducting states is analogous to what occurs in a conventionalelectric generator, whereby a current is generated in electricallyconductive windings which move relartive to a magnetic field. A givenportion of the windings “sees” a varying magnetic field strength as thewindings move.

In a fourth embodiment, illustrated in FIG. 10, part of the currentgenerated in the wire or coil 122 could be used in a feedback mode toactuate a liquid crystal shutter 130 which alternately intercepts andpasses solar radiation directed towards the superconducting article. Theshutter 130 could be controlled by a conventional rectifying circuit 132that would deliver a unidirectional current varying between zero andsome upper limit. With the current at the upper limit, as in FIG. 10(a),the shutter 130 would be dark, therefore intercepting radiation andallowing the article to cool below T_(c). With the current at zero, asin FIG. 10(b) the shutter 130 would be clear, thus passing radiation tothe article so that it would heat to above T_(c).

In a fifth embodiment shown in FIG. 11, electrical power is generated byvia a piezoelectric body 134. The superconducting article 100 and themagnet 104 are spaced within interactive range of each other, and eitherof them connected to the piezoelectric body so that it can exert avarying pressure thereon in response to article 100 going in and out ofthe superconducting state. The wire 122 is connected to thepiezoelectric body 134 and the electrical current generated therein canbe registered on the meter 124.

The various embodiments and modifications describe above are notintended to be exhaustive. For example, any embodiment could be used incombination with any appropriate masking or shuttering device. While theinvention has been shown and described with particularity, it will beappreciated that various changes and modifications may suggestthemselves to one having ordinary skill in the art upon being apprisedof the present invention. It is intended to encompass all such changesand modifications as fall within the scope and spirit of the appendedclaims.

1. A method for generating energy using a superconductor, comprising:(a) generating a magnetic field having a field strength; (b) locatingthe superconductor so it can reversibly interact with the magneticfield; (c) causing the superconductor to change between asuperconducting and a non-superconducting state, thus causing a changein the magnetic field strength; and (d) coupling the magnetic field witha movable member responsive to the changing magnetic field strength. 2.The method of claim 1, further comprising cooling and heating thesuperconductor through a transition temperature Tc defined by atransition between the states.
 3. The method of claim 1, furthercomprising cooling the superconductor by immersing it in a cooling bathand heating it by allowing it to emerge from the cooling bath.
 4. Themethod of claim 3, including using liquid nitrogen for the cooling bathand further including using an YBCO superconductor.
 5. A method forgenerating energy, comprising: (a) generating a magnetic filed with amagnet, the magnetic filed having a magnetic field strength; (b)disposing a superconducting article so it can interact with the magneticfield, the article having a non-superconductive state above Tc and asuperconductive state below Tc; (c) cooling and heating thesuperconducting article through Tc, thus causing a fluctuation in themagnetic field strength; and (d) coupling the magnetic field with amovable member responsive to the fluctuating magnetic field strength. 6.The method of claim 5, further comprising allowing one of the magnet andthe article to reversibly move between a near and a distal positionrelative to the other.
 7. The method of claim 6, including connectingthe member with one of the magnet and the article which is allowed tomove.
 8. A method for generating energy using an interaction between asuperconductor and a magnetic field with a field strength, thesuperconductor being capable of a reversible transition between asuperconducting and a non-superconducting state, the method comprising:(a) cyclically effecting a plurality of the transitions between thestates, thus causing the magnetic field strength at a given point tofluctuate; and (b) coupling the magnetic field with a member which isreversibly movable in response to the fluctuation in magnetic fieldstrength.